The objective of this study is to examine the cancer mortality experience in the United States relative to cancer etiology. Special emphasis is placed upon the selection of areas in the U.S. for intensive study. Publications from this area of interest have facilitated the design of ongoing analytical investigation to test specific etiologic hypotheses. Possible prenatal origins of childhood cancer are being investigated by focusing on potential exposures realized by the pregnant mother. The rising rates of myeloma in blacks suggest genetic and environmental factors that need to be tested in analytic epidemiologic studies. Analysis of non-Hodgkin's lymphoma at the county level for 1950-1975 detected associations with higher social class and also large percentages of residents of Russian and Greek descent. Changes in age-specific rates for breast cancer appear related to the changing patterns of childbearing among young adult women of the first two-thirds of this century. Analyses of changing patterns in the rates of thyroid cancer in Connecticut detected findings consistent with the use of radiation therapy from the early 1920's to the late 1950's.